Here is another reference to add to the possible context from which these chanty forms emerged.

It is John Lambert's TRAVELS THROUGH CANADA AND THE UNITED STATES...VOL. III, published in 1810.

The event referred to, I believe, happened in 1806. The narrator is going by boat down the Savannah River.

We started from Purrysburgh about two o'clock and were rowed by four negroes, for canoes are not paddled here as in Canada. They seemed to be jolly fellows, and rowed lustily to a boat song of their own composing. The words were given out by one of them, and the rest joined chorus at the end of every line. It began in the following manner:

Chorus.

" We are going down to Georgia, boys,
CH: Aye, aye,

To see the pretty girls, boys ;
CH: Yoe, yoe.

We'll give 'em a pint of brandy, boys,
CH: Aye, aye.

And a hearty kiss besides, boys.
CH:Yoe, yoe.            
&c. &c.

The tune of this ditty was rather monotonous, but had a pleasing effect, as they kept time with it, at every stroke of their oars. The words were mere nonsense ; any thing, in fact, which came into their heads. I however remarked, that brandy was very frequently mentioned, and it was understood as a hint to the passengers to give them a dram.

Note again the incidental nature of the text. It is impossible to identify this as the progenitor to any one specific chantey, however the basic form is that of a chantey and the ad-libbed nature is also in keeping with the tradition. Again, no analogy is made to other work-song practices in the author's own tradition or aboard sailing vessels.

More boat/rowing references to come, as that seems to be where these sorts of songs were used at this point in time.